VEHICLE MISSIONS: These missions require a certain type of vehicle and are triggered by pressing R3 (the right analog stick). They occur on and around the area where you start them. So, logically, you'll want to start in an area that's easy to navigate and traverse. The airport is a good location for many of these missions.

VIGILANTE Reward: Maximum armor value raised to 150 when level 12 is completed
Vehicle: Any law enforcement or military vehicle

Description: Criminals on the lam will appear on your radar, and it's your job to take them out using whatever means necessary. Time is gained by successfully eliminating targets. The mission ends when you run out of time or fail to return to a police vehicle during the mission. While it's possible to perform these missions in a police car or FBI vehicle, you can really breeze through them with a military vehicle such as the Rhino or Hunter and So on................................